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RDFa

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RDF is defined as an abstract data model, plus a collection of practical notations for exchanging RDF descriptions (eg. RDF/XML, RDFa, Turtle/N3). In theory, your data modelling activities are conducted in splendid isolation from the sleazy details of each syntax. RDF vocabularies define classes of thing, and various types of property/relationship that link those things. And then instance data uses arbitrary combinations of those vocabularies to make claims about stuff. Nothing in your vocabulary design says anything about XML or text formats or HTML or other syntactic details.

All that said, syntactic considerations can mess with your modelling. I’ve just written this up for the Linked Library Data group, but since the point isn’t often made, I thought I’d do so here too.

RDF instance data, ie. descriptions of stuff, is peculiar in that it lets you use multiple independent schemas at the same time. So I might use SKOS, FOAF, Bio, Dublin Core and DOAP all jumbled up together in one document. But there are some considerations when you want to mention that something is in multiple classes. While you can do this in any RDF notation, it is rather ugly in RDF/XML, historically RDF’s most official, standard notation. Furthermore, if you want to mention that two things are related by two or more specified properties, this can be super ugly in RDF/XML. Or at least rather verbose. These practical facts have tended to guide the descriptive idioms used in real world RDF data. RDFa changes the landscape significantly, so let me give some examples.

Backstory – decentralised extensibility

RDF classes from one vocabulary can be linked to more general or specific classes in another; we use rdfs:subClassOf for this. Similarly, RDF properties can be linked with rdfs:subPropertyOf claims. So for example in FOAF we might define a class foaf:Organization, and leave it at that. Meanwhile over in the Org vocabulary, they care enough to distinguish a subclass, org:FormalOrganization. This is great! Incremental, decentralised extensibility. Similarly, FOAF has foaf:knows as a basic link between people who know each other, but over in the relationship vocabulary, that has been specialized, and we see relationships like ‘livesWith‘, ‘collaboratesWith‘. These carry more specific meaning, but they also imply a foaf:knows link too.

This kind of machine-readable (RDFS/OWL) documentation of the patterns of meaning amongst properties (and classes) has many uses. It could be used to infer missing information: if Ian writes RDF saying “Alice collaboratesWith Bob” but doesn’t explicitly say that Alice also knows Bob, a schema-aware processor can add this in. Or it can be used at query time, if someone asks “who does Alice know?”. But using this information is not mandatory, and this creates a problem for publishers. Should they publish redundant information to make it easier for simple data consumers to understand the data without knowing about the more detailed (and often more recent) vocabulary used?

Historically, adding redundant triples to capture the more general claims has been rather expensive – both in terms of markup beauty, and also file size. RDFa changes this.

RDFa 1.0 requires the second vocabulary’s namespace to be declared, but after that it is pretty concise if you want to throw in a 2nd or a 3rd type, for whatever you’re describing. If you’re talking about a relationship between people, instead of ” rel=’foaf:knows’ ” you could put “rel=’foaf:knows rel:livesWith’ “; if you wanted to mention that something was in the class not just of organizations, but formal organizations, you could write “typeof=’foaf:Organization org:FormalOrganization'”.

Properties and classes serve quite different social roles in RDF. The classes tend towards being dull, boring, because they are the point of connection between different datasets and applications. The detail, personality and real information content in RDF lives in the properties. But both classes and properties fall into specialisation hierarchies that cross independent vocabularies. It is quite a common experience to feel stuck, not sure whether to use a widely known but vague term, or a more precise but ‘niche’, new or specialised vocabulary. As RDF syntaxes improve, this tension can melt away somewhat. In RDFa it is significantly easier to simply publish both, allowing smart clients to understand your full detail, and simple clients to find the patterns they expect without having to do schema-based processing.

First reaction above all, is that this is great news! Very happy to see this work maturing.

I’ve tried to quickly suggest some tweaks to the vocab, by hacking his diagram in photoshop. All it really shows is that I’ve forgotten how to use photoshop, but I’ll upload it here anyway.

So if you click through to the full image, you can see my rough edits.

I’d suggest:

Use (dcterms) dc:subject as the way of pointing from a document to it’s SKOS subject.

Use (dcterms) dc:creator as the relationship between a document and the person that created it (note that in FOAF, we now declare foaf:maker to map as an equivalentProperty to (dcterms)dc:creator).

Distinguish between the description of the person versus their account in the Drupal system; I would use foaf:Person for the human, and sioc:User (a kind of foaf:OnlineAccount) as the drupal account. The foaf property to link from the former to the latter is foaf:account (new name for foaf:holdsAccount).

Focus on SIOC where it is most at-home: in modelling the structure of the discussion; threading, comments and dialog.

Provide a generated URI for the person. I don’t 100% understand Stephane’s comment, “Hash URIs for identifying things different from the page describing them can be implemented quite easily but this case hasn’t emerged in core” but perhaps this will be difficult? I’d suggest using URIs ending “userpage#!person” so the fragment IDs can’t clash with HTML usage.

If the core release can provide this basic structure, including a hook for describing the human person rather than the site-specific account (ie. sioc:User) then extensions should be able to add their own richness. The current markup doesn’t quite work for that end, as the human user is only described indirectly (unless I understand current reading of sioc:User).

Anyway, I’m nitpicking! This is really great, and a nice and well-deserved boost for the RDFa community.

This blog post isn’t signed, the URIs it referenced don’t use SSL, and the image could be switched by evildoers at any time! But the question’s worth asking: is this kind of scruffy key info useful, if there’s enough of it? If I wrote it somehow in Thunderbird’s editor instead, would it be easier to sign? Will 99.9% of humans ever know enough of what’s going on to understand what signing a bunch of complex markup means?

For earlier discussion of this kind of thing, see Joseph Reagle’s Key-free Trust piece (“Does Google Show How the Semantic Web Could Replace Public Key Infrastructure?”). It’s more PKI-free trust than PK-free.

So, where are we here? We see two RDF datasets about the same school. One is the simple claim that I attended the

school at some time in the past (1976-1978, in fact). The other describes many of its current attributes; most of which may be different now from in the past. In my sample RDFa, I used the most popular Web link for the school to represent it; in the Edubase government data, it has a Web site address but it seems not to be current.

Assuming we’d used the same URIs for the school’s homepage (or indeed for the school itself) then these bits of data could be joined.

Perhaps a more compelling example of data linking would be to show this schools data mixed in with something like MySociety’s excellent interactive travel maps? Still, the example above shows that basic “find people who went to my school” queries should be very possible…

FOAF has always had a bias towards describing social things that are shown rather than merely stated; this is particularly so in matters of trust. One way of showing basic confidence in others, is by accepting their comments on your blog or Web site. F2F is an experiment in syndicating information about these kinds of everyday public events. With F2F, others can share and re-use this sort of information too; or deal with it in aggregate to spread the risk and bring more evidence into their trust-related decisions. Or they might just use it to find interesting people’s blogs.

OpenID is a technology that lets people authenticate by showing they control some URL. WordPress blogs that use the OpenID plugin slowly accumulate a catalogue of URLs when people leave comments that are approved or rejected. In my previous post I showed how I was using the list of approved OpenIDs from my blog to help configure the administrative groups on the FOAF wiki.

This may all raise more questions than it answers. What level of detail is appropriate? are numbers useful, or just lists? in what circumstances is it sensible or risky to merge such data? is there a reasonable use for both ‘accept’ lists and ‘unaccept’ lists? What can we do with a list of OpenID URLs once we’ve got it? How do we know when two bits of trust ‘evidence’ actually share a common source? How do we find this information from the homepage of a blog?

If you install the F2F plugin (and have been using the OpenID plugin long enough to have accumulated a database table of OpenIDs associated with submitted comments), you can experiment with this. Basically it will generate HTML in RDFa format describing a list of people . See the F2F Wiki page for details and examples.

The script is pretty raw, but today it all improved a fair bit with help from Ed Summers, Daniel Krech and Morten Frederiksen. Ed and Daniel helped me get started with consuming this RDFa and SPARQL in the latest version of the rdflib Python library. Morten rewrote my initial nasty hack, so that it used WordPress Shortcodes instead of hardcoding a URL path. This means that any page containing a certain string – f2f in chunky brackets – will get the OpenID list added to it. I’ll try that now, right here in this post. If it works, you’ll get a list of URLs below. Also thanks to Gerald Oskoboiny for discussions on this and reputation-related aggregation ideas; see his page on reputation and trust for lost more related ideas and sites. See also Peter Williams’ feedback on the foaf-dev list.

Next steps? I’d be happy to have a few more installations of this, to get some testbed data. Ideally from an overlapping community so the datasets are linked, though that’s not essential. Ed has a copy installed currently too. I’ll also update the scripts I use to manage the FOAF MediaWiki admin groups, to load data from RDFa blogs; mine and others if people volunteer relevant data. It would be great to have exports from other software too, eg. Drupal or MediaWiki.

I’m writing this in WordPress’s ‘Visual’ mode WYSIWYG HTML editor, and thinking “how could it be improved to support RDFa?”

Well let’s think. Humm. In RDFa, every section of text is always ‘about’ something, and then has typed links or properties associated with that thing. So there are icons ‘B’ for bold, ‘I’ for italics, etc. And thingies for bulleted lists, paragraphs, fonts. I’m not sure how easily it would handle the nesting of full RDFa, but some common case could be a start: a paragraph that was about some specific thing, and within which the topical focus didn’t shift.

So, here is a paragraph about me. How to say it’s really about me? There could be a ‘typeof’ attribute on the paragraph element, with value foaf:Person, and an ‘about’ attribute with a URI for me, eg. http://danbri.org/foaf.rdf#danbri

In this UI, I just type textual paragraphs and then double newlines are interpreted by the publishing engine as separate HTML paragraphs. I don’t see any paragraph-level or even post-level properties in the user interface where an ‘about’ URI could be stored. But I’m sure something could be hacked. Now what about properties and links? Let’s see…

I’d like to link to TinyMCE now, since that is the HTML editor that is embedded in WordPress. So here is a normal link to TinyMCE. To make it, I searched for the TinyMCE homepage, copied its URL into the copy/paste buffer, then pressed the ‘add link’ icon here after highlighting the text I wanted to turn into a link.

It gave me a little HTML/CSS popup window with some options – link URL, target window, link title and (CSS) class; I’ve posted a screenshot below. This bit of UI seems like it could be easily extended for typed links. For example, if I were adding a link to a paragraph that was about a Film, and I was linking to (a page about) its director or an actor, we might want to express that using an annotation on the link. Due to the indirection (we’re trying to say that the link is to a page whose primary topic is the director, etc.), this might complicate our markup. I’ll come back to that later.

tinymce link edit screenshot

I wonder if there’s any mention of RDFa on the TinyMCE site? Nope. Nor even any mention of Microformats.

Perhaps the simplest thing to try to build into TinyMCE would be for a situation where a type on the link expressed a relationship between the topic of the blog post (or paragraph), and some kind of document.

For example, a paragraph about me, might want to annotate a link to my old school’s homepage (ie. http://www.westergate.w-sussex.sch.uk/ ) with a rel=”foaf:schoolHomepage” property.

So our target RDFa would be something like (assuming this markup is escaped and displayed nicely):

See recent discussion on the foaf-dev list where we contrast this idiom with one that uses a relationship (eg. ‘school’) that directly links a person to a school, rather than to the school’s homepage. Toby made some example RDFa output of the latter style, in response to a debate about whether the foaf:schoolHomepage idiom is an ‘anti-pattern’. Excerpt:

My name is <span property=”foaf:name”>Dan Brickley</span> and I spent much of the ’80s at <span rel=”foaf:school”><a typeof=”foaf:Organization” property=”foaf:name” rel=”foaf:homepage” href=”http://www.westergate.w-sussex.sch.uk/”>Westergate School</a>.

</p>

So there are some differences between these two idioms. From the RDF side they tell you similar things: the school I went to. The latter idiom is more expressive, and allows additional information to be expressed about the school, without mixing it up with the school’s homepage. The former simply says “this link is to the homepage of Dan’s school”; and presumably defers to the school site or elsewhere for more details.

I’m interested to learn more about how these expressivity tradeoffs relate to the possibilities for visual / graphical editors. Could TinyMCE be easily extended to support either idiom? How would the GUI recognise a markup pattern suitable for editing in either style? Can we avoid having to express relationships indirectly, ie. via pages? Would it be a big job to get some basic RDFa facilities into WordPress via TinyMCE?

Fancy title but simple code. A periodic update script is setting user/group membership rules on the FOAF wiki based on a list of trusted (for this purpose) OpenIDs exported from a nearby blog. If you’ve commented on the blog using OpenID and it was accepted, this means you can also perform some admin actions (page deletes, moves, blocking spammers etc.) on the FOAF wiki without any additional fuss.

Both WordPress blogs and Mediawiki wikis have some support for OpenID logins.

The FOAF wiki until recently only had one Sysop and Bureaucrat account (a bureaucrat has the same privileges as a Sysop except for the ability to create new bureaucrat accounts). So I’ve begun an experiment exploring idea of pre-approving certain OpenIDs for bureaucrat activities. For now, I take a list of OpenIDs from my own blog; these appear to be just the good guys, but this might be because only real humans have commented on my blog via OpenID. With a bit of tweaking I’m sure I could write SQL to select out only OpenIDs associated with posts or comments I’ve accepted as non spammy, though.

So now there’s a script I can run (thanks tobyink and others in #swig IRC for help) which compares an externally supplied list of OpenID URIs with those OpenIDs known to the wiki, and upgrades the status of any overlaps to be bureaucrats. Currently the ‘syndication’ is trivial since the sites are on the same machine, and the UI is minimal; I haven’t figured out how best to convey this notion of ‘pre-approved upgrade’ to the people I’m putting in an admin group. Quite reasonably they might object to being misrepresented as contributors; who knows.

But all that aside, take a look and have a think. This kind of approach has a lot going for it. We will have all kinds of lists of people, groups of people, and in many cases we’ll know their OpenIDs. So why not pool what we know? If a blog or wiki has information about an OpenID that shows it is somehow trustworthy, or at least not obviously a spammer, there’s every reason to make notations (eg. FOAF/RDFa) that allow other such sites to harvest and integrate that data…

See also Dan Connolly’s DIG blog post on this, and the current list of Bureaucrats on the FOAF Wiki (and associated documentation). If your names on the list, it just means your OpenID was on a pre-approved list of folk who I trust based on their interactions with my own blog. I’d love to add more sources here and make it genuinely communal.

This is all part of the process of getting FOAF moving again. The brains of FOAF is in the IssueTracker page, and since the site was damaged by spammers and hackers recently I’m trying to make sure we have a happy / wholesome environment for maintaining shared documents. And that’s more than I can do as a solo admin, hence this design for opening things up…

This kind of technology is not limited to global search. On a social networking site built with Drupal, it opens up the possibility to do all sorts of deep social searches – searching by types and levels of relationships while simultaneously filtering by other criteria. I was talking with David Peterson the other day about this, and if Drupal core supported FOAF and SIOC out of the box, you could search within your network of friends or colleagues. This would be a fundamentally new way to take advantage of your network or significantly increase the relevance of certain searches.

Meanwhile, PHP Shindig (Apache’s OpenSocial widget container) has now been integrated into Drupal. Currently version 5 but things are moving to get it working in 6.x too. See docs (this link has some issues) and the announcement/discussion from shindig-dev. Also great news…

The are some interesting things going on at Mozilla Labs. Yesterday, Ubiquity was all over the mailing lists. You can think of it as “what the Humanized folks did next”, or as a commandline for the Web, or as a Webbier sibling to QuickSilver, the MacOSX utility. I prefer to think of it as the Mozilla add-on that distracted me all day. Ubiquity continues Mozilla’s exploration of the potential UI uses of its “awesome bar” (aka Location bar). Ubiquity is invoked on my Mac with alt-space, at which point it’ll enthusiastically try to autocomplete a verb-centric Webby task from whatever I type. It does this by consulting a pile of built-in and community-provided Javacript functions, which have access to the Web, your browser (hello, widget security fans)… and it also has access to UI, in terms of an overlaid preview window, as well as a context menu that can actually be genuinely contextual, ie. potentially sensitive to microformat and RDFa markup.

So it might help to think of ubiquity as a cross between The Hobbit,GreaseMonkey, Bookmarklets, and Mozilla’s earlier forms of packaged addon. Ok, well it’s not very Hobbit, I just wanted an excuse for this screen grab. But it is about natural language interfaces to complex Webby datasources and services.

The basic idea here is that commands (triggered by some keyword) can be published in the Web as links to simple Javascript files that can be single-click added (without need for browser restart) by anyone trusting enough to add the code to their browser. Social/trust layers to help people avoid bad addons are in the works too.

I spent yesterday playing. There are some rough edges, but this is fun stuff for sure. The emphasis is on verbs, hence on doing, rather than solely on lookups, query and data access. Coupled with the dependency on third party Javascript, this is going to need some serious security attention. But but but… it’s so much fun to use and develop for. Something will shake out security-wise. Even if Ubiquity commands are only shared amongst trusting power users who have signed each other’s PGP keys, I think it’ll still have an important niche.

What did I make? A kind of stalk-a-tron, FOAF lookup tool. It currently only consults Google’s Social Graph API, an experimental service built from all the public FOAF and XFN on the Web plus some logic to figure out which account pages are held by the same person. My current demo simply retrieves associated URLs and photos, and displays them overlaid on the current page. If you can’t get it working via the Ubiquity auto-subscribe feature, try adding it by pasting the raw Javascript into the command-editor screen. See also the ‘sindice-term‘ lookup tool from Michael Hausenblas. It should be fun seeing how efforts like Bengee’s SPARQLScript work can be plugged in here, too.